Automatic intercommunicating telephone system



July 30, 1935. o. M. LEIGH 2,009,405

AUTOMATIC INTERCOMMUNICATING TELEPHONE SYSTEM Filed Sept. 29, 1933 Tilf/f/WVE Wag/ Patented July 30, 1935: 3, y r

UNITED ims Oscar e oii, Genoa, m, assigno'r to Leioh Electric 00., Genoa, 111.; a corporation of Illinois v r 1 Application September 29,1933, Serial No. 6915231 f9 Claims. (01. I'll-16b My invention relates to automatic intereqmternating current for ringing is applied at sixty municating telephone systems, and hes for its velts through the terminals 19; and 20. Direct principal object the provision of a system of current-from the battery is utilized for operating character which permits the operator of any one andntalking'. 'Ihe battery is not shown, but the '5 of several telephones to select and talk to any appropriate polarity has been shown by the usual other one of the group with utilization of only at positive and negative signs wherever battery conthe most three line connections for each. telenections are made; The operating relays B, S phone two of which connections are commonv to and I areoperated from the telephone initiating all telephones. I thecall.- fI'hese relays in turn control the oper-' It is also a purpose of my invention to provide ationofthe four. relays A! to A4 inconjunct n 10- a system of this character which gives to telewith theindividual line relays CI, to Q5 inclusive. phones of the system full selective ringing of the Relay R is an alternating current relay. Allof others by means of a pair of push buttons at each the equipment is sho n at rest which isthe positelephone'. tion when no call is taking place. y It is also an object of this inventionto provide Itis believed that the operation of the system a system of this character in which the number will be best understoodby. describing in detail the of telephones on the system can be increased steps that take place when a call is madev from or decreased without changing the equipment at one station to another. I v each telephone and with the addition orremoval' We will that telephone I is initiating a of very little equipment at the central station. call. ;Liiting ei this telephone from its base closes 2 Other and more specific objects and advantages the two hook switch contacts I! and I 8 which or the invention will appear as the description D YidB -theiQll s i .circuitior reproceeds in connection with. the accompanying 1ays; B,- I; and S; An energizing circuit for relay drawing wherein the preferred form of the im rom negative bae y throughi vention is shown. It is to be understood; how-: 50 ohrnwindglof B relay to line L2 and over ever, that the drawing and description areillus-i this line conductor through the lower hook switch trative only and are not to be taken as limiting contact 18 through lower contact 2! on a the invention except'in so far asit is limited by selectinggkey; l3, through thehand set receiver the claims.- a i I0 and transmitter H to the line LI and over this In the drawing-- g 3 line .oonductor to the 25 ohm winding of I relay 0 Fig. l is a diagrammatic view of the system; topositive battery. ;Also, relay S is energized and over va circuit extending from negative battery Fig. 2 is asmall view illustrating the application through the 150 7 ohm ;.w,i nding of. the S relay of a biasing spring to the ringing bell. mmugh the break contact Lon relay CI to line Referring now in detailto the-drawing,- I have G and over line-G t t e closed Contact of t e 35- shown my invention as applied to, asys'tem in; ringing :push button 14. which is adapted to be eluding five telephones of whichonly tW0,-NOS. opened by pressure onthe' push button, then I and 4, are shown. Since the equipment atall through the upper hook switch contacts H. to telephones is the same, it is believed that this will line L1 and over this line conductor to relay I 40 be suflicient to enable one to understand the and: through the winding of relay I to positive 40 operation of the system. At each telephone there battery. I is areceiver I0 and a transmitter, H connected *From' he-d scr P n-t it Will e ee in series across the line wires LI and L2 to: hook that I r lay ism i uit with r ay B and r ay S switch l2. There is also at each telephone a s'e-f so that the circuit of either of them may be broken lecting key 13 and a ringing key M together with and relay I will continuetoiibe energized through 45 a bell l5, and in series with the bell is: a small the other.; At this point it will be well to recall condenser l6 which may be of about one half that relay I wilinotzbeenerg ized until relay B has mi. capacity. Lines LI and L2 are common to been energized since break contact No. l of relay all telephones, and each-individual telephone is Biconnects'Ll topositive battery over break conprovided with a third line G so I have: shown five tMtviNO-, 21 of relay 1. a 50 r of these lines, GI to G5. thethreerelays B, .I, andShave been I Hook switch 12 is so arranged as to closzits energizedz's dmoribd, this c'iomplctesv a circuit upper contact -I'l before closing contact.- IS in all for operatmg relay A3. over thefoi'lowir'ig circuit:

the I negative battery: at relay C5 on its break 66. Referring now to the operating equipment, a1= contact Nor then over each ofithe breakv con- 2 tacts of the five C relays in turn to the inside winding of relay A3, then over conductor 22 to front contact No. 2 of relay B and front contact No. 2 of relay I to positive battery. This prepares the equipment for the selecting operation. The operator'at telephone I makes the selection by depressing the select button 13 a number of times, the number depending upon which of the other telephones he wishes to select. 'The first operation in pressing the select button I3 is to establish a short circuit around the transmitter l0 and the receiver l I over contact 23 and line '24. This shunts the inductive discharge of there'lay coilsand thus prevents un'necessarynoise in the operators ears. Also, the break contactjof the select push button opens the circuit of relay B at contact 2 I, and this causes the operation of relay A2 and relay Cl over the following circuit: From" positive battery and front contact 2 of-relay I to back contact No.2 of relay B, then over line 25 to back contact No. I of relay Al' and-over line 26 and branch line 21to the inside winding of relay A2 and then t'o' negative battery, also over line 26 andbranch line 28 to inside winding of relay- C|- and to negative battery.-

Relay A2 locks itself energized'over the following circuit: From negative battery on line 30 over branch line 29 to outside winding of relay A2 then through front contact No. l ofrelay A2 and front contact No." 2 of relay A3, andthen over line 3| to front contact No. -2'-of relay I and positive battery. 7

Relay CI locks itself energized over the following path: From positive battery through front I contact No. 2 of relay I over line 3| to branch line 32, which is common to the outside windings of all the C relays, through outside-winding of relay CI to front contact 3 of relayCt and'then through break contacts No. 3 of relay's'C2 to C5 inclusive to negative battery. The-spring 'armaturesof the C relays are such that, as Cl is energized, the circuit'of relay s isnot interrupted since front contact No. Iof Cl relay makes before the break contact of this relay opens, thus connecting GI to line 33 before breaking the connection to line34. V 4 f Y When the select button 13 is restored to normal; relay B again operates, and this resultsin the operation of relay Al over the following path: From positivebattery, through-front contact No. 2 of relay I, to front contact No; 2 of relay B, then over line 22 to front'co'ntactNo. 2- of relayA2, and then to inside-winding of relay Al and nega-'- tive battery. The'energ'izing of relay Al opens the locking circuit for relay A3-by breaking the circuit'at contact 3 of relay Al-so relay A3 is re-' leased, and this breaks the hold circuit for relay A2 at front contact No; 3 of relay A3. 3

Relay Al locks itself energized over the following path: From negative battery to outside winding of relay Al, through front contact No. 2 of relay Al, over line 35 to back contact No; 20f relay A3, and back contact No. 3 of relay A4 to line 3|, and overline 3|, to positive battery at front contact No. 2 of relay I When the select button isagain operated, relay B is released, and thisoperates relay A4. over the following path Frompositive battery through front contract No. 2 of relay'I, :and back' co'ntact No. 2 of relay B, to line 25, through front contact No. Iiof relay Al, to line 36, and branchline 31 to inside winding of relay A4. andnegative battery.

Relay A4 locks energized overthe' following path: From positive battery through front con-'- tact No.. 2 of relay I, overzline 3fitolback contact negative battery. Relay C2 is locked energized over a circuit extending from positive battery through front contact No.2 of relay I, over lines 3| and 32 to outsidewinding of relay C2, front contact No. 3 of relay C2, and break contacts No. 3 of relays C3 to C5 to negative battery. This operation releases relay Cl since its locking circuit is open at break contact No; 3 of relay C2.

When the select button is restored to normal, relay B again operates.

' Relay A3 is energized over a line extending from positive battery through front contact 2 of relay I;

front contact2 of relay B, line 22 to inside winding of relay A3, lines 39 and 40 to front contact 2 of relay A4, and line 30 to negative battery. Relay AI is released since its locking circuit is opened'at back contact'2 of relay A3 and back conta'ct3 of relay A4; 3 Upon the next push of the select button 13, relay B is again deenergized, and this causes the operation of A2 over the following circuit: From positive battery'and front contact No. 2 of relay I,'through back contact 2 of relay B, over line 25, and back contact I of relay AI, through lines 26 and 21 and inside winding of relayA2 to negative battery. 7 r

Relay A2 locks energized through its outside winding over a circuit extending from negative battery over line 30 and line 29 through outside winding of relay A2,- front contact No. I of relay A2, front contact No; 2 of relay A3, line 3|, front contact 2 ofrelay I to positive battery. RelayCl is momentarily energized over line 26 and branch line to negative battery by the connection of positive battery to line 25, but this does 'not affect the further operation as Cl cannot lock itself {energized at this time owing to the fact that its locking circuit is broken at back contact 3 of relay C2. Relay A4 is released at the contact 3 of A2.

' Relay C3 is energized over a circuit which may be traced from positive battery through front contact 2' of relay I, back contact 2 of relay B, line 25, back contact I of relay Al, line 26, to contact 2 'on relay C2, and inside winding'of relay C3 to negative batteryf Relay C3 locks energized over a circuit extending from positive battery over front contact 2 of relay I, lines 3l and 32, outside winding of relay C3, front contact 3 of relay C3, and break contact-No. 3 of relay C4 and C5 to negative battery. This breaks'the locking circuit of relay C2 at the break contact 3 of C3 to'deenergize relay C2.. i U When the select button is returned 'to-normal, relay B again operates, and relay Al is energized over the following path: From positive battery through front contact 2 of relay I, frontcon tact 2 of'relay B, line 22, front contact 2 of relay A2, and inside winding of relay Al to negae tive battery. .i

Z'I'heflocking circuit of relay A3-.is broken'at contact 3 of relayAI, so relay A3 releases, thus breaking the locking circuit of relay A2 at front contact. 2 of relayA3. i

ture and energize-relay- S. If the operator at 'ReIay Ailocks energized over a circuit from a telephone 1 releases theringing button?! 4, the

negative battery over-line 30, through the outside winding of relay Al, front'con'ta'ct' 2 of relay Al, line 35, to 'back'contact2 of A3, and back con tact 3 of A4, and then over line 3! to frontcontact" 2 of relay I and positive battery.

When select button I3 is again operated, relay B releases andrelay A4'operates over the following circuit: From positive battery'through front contact 2 of relayI, backcontact 2 of relayB, line-25, 'frontcontact l of relay Al, lines 36 and'3'l, to inside winding-of relay A4 to negative battery. Relay A4 locks energized from positive battery over line 3|, through back contact 3 of A2,'front-contact I of A4, outside winding of A4 to negative battery over line-30. y A 'Relay C4 is-also-energized at this time from positive battery over front contact 2 of relay I,-

back contact 2 of relay B, line 25,'line 38, front 20 contact 2 of relay C3, to inside winding of relay C4, and negative battery. Relay C4'locks ener gized over a circuit extending frompositive battery through front contact 2 of relay I, over lines 3| and 32, to outside winding of C4; front conta'ot3 of relay C4, and break contact 3 of-relay C5 to negative battery. This breaks the energizing circuit for relay G3 at break contact 3 of relay C4 so relay C3 is deenergized.

When the select button I 3 is restored to normal, relay B is again energized, and relay A3 is -energized over a circuit extending from positive battery through front'contact 2 of relay I, front contact 2 of relay B, line 22, inside winding of relay A3, lines 39 and 40, front contact 2 of relay A4, and line '30 to negative battery. Relay Al is released since its locking circuit is opened at back-contact 3 of relay A4, and back contact 2 of relay A3. In this manner relay G4, which is connected to the individual line wire G4, has been selected by'four depressions of the select button I3 and is now locked and 'ready'to signal No. 4 telephone. -At'this time it will be noted that relay C4 is held operated as long as relay I is energized to maintain positive battery on front contact 2 of relay I.- Relays A3 and A4 are also held operated so long as relay I main-' tains positive battery on front contact 2. These, however, are necessary only if continued selections are to be made.

To ring No. 4 telephone, the personmaking the call at No. I telephone pushes the ringing button l4. This opens the operating circuit of relay S which'is energized, over a path extending from positive battery through winding of relay I 1 over Ll, contact 41, hook switch l2, contacts on ringing key l4, line GI, break contact I of relay Cl, line 34 to winding of relay S and negative battery. Relay I is still held energized in series with relay B even though relay S is deenergized.

Relay S being released supplies one side of ringing current from terminal l9, through back contact I of relay S, front contact I of relay I, common line Ll, to tap T4 and line, through one-half mfd. condenser [6 to one side of bell l5 of telephone 4.

The other terminal 20 for supplying ringing current is connected through the 100 ohm winding of A. C. relay R, over back contact 2 of relay S, over line 33, to front contact I of relay C4, line G4, to the other side of bell l5 of telephone 4. The bell [5 .at telephone 4 will ring as long as ringing button l4 at the calling telephone is held down, because the current which can flow through bell l5 and condenser I6 is insufficient to cause relay R to attract its armatelephone 4 at contact I of relay S. Thus if more 7 than one telephone is connected on one line, a code may be used to'signal either telephone.

'-' wnen the-party at telephone 4 answers, the

hook switch l2 of telephone 4 closes; its contacts I! closing firstto shunt-the bell li of telephone 4 by closing a circuit from line-G4 through closed contacts 'of ringing button l4and contacts I! of:

telephone 4 toterminal T4 on line Ll. Relay R; is energized over this shunt circuit as follows: from terminal 19 through break contact I, of relay S; front contact I' of relay I, line Ll to;.T4, then through closed contacts H of switch l2 and ringing key M at telephone No. 4, over lineG4-to.

frontcontactl of relay C4 over line, through break contact2 of relay S, and winding of relay R toterminal 20.; This shunt circuit also provides'a circuit to energize relay S as follows: From positive battery at relay I, through winding of relay I, line Ll to terminal T4, contacts ll of tele-' phone 4, contacts of ringing button I4 of telephone 4, line G4, make contact I of relay C4, line 33, to

contact 2 'of relay S. Then when relay R-attracts its armature to momentarily energize relay 3 from positive battery through 50 ohm, resistance 42, contact of relay R, and winding of relay S to negative battery, contact is'made at front contact 2 of relay S, and line 33 is thereby connected through this contact to winding'of relay S tonegative battery.

Both-parties-arenow connected across talking lines Li, L2. 7 a When both parties hang up, contacts l1 and i8 at both telephones are opened, and the holding circuits of relays B, S, and I are broken thus re-- leasing these relays. Release of relay I breaks the holding circuits for all other relays, releasing them and returning the system to rest.-

In Fig. 2, I have shownsomewhat diagrammatically a bell box l5 to illustrate the use of a biasing-spring 43 on the bell arm 44 for prevent- .ing tapplngof the bells when a call was being made. The purpose of spring 43 is to hold the arm 44 in the position shownduring the calling and selecting until the ringing button is operated, and thus avoid the taps of the bells whena call ismade.-' a

The condenser IS in the bell ringing line of each telephone also protects the battery of the system from running down in case of wrong connections of the three lines leading from the telephone to the central station.. Since the bell is connectedacross the lines to be attachedto GI and Li, and batteryacross LI and L2, it is evident that, if the line that should be connected to GI is improperly connected so as to put the battery across the bell terminals, the battery might well be run down before the mistake was located.

It is believed that the manner of connecting and I plurality of telephones, a ringing bell for each.

telephone, a selecting switch and a ringing switch at each telephone, a pair of line conductors common to all telephones, and an individual con ductor for each telephone, a central station to 75 I which said conductorslead, said stationhaving means'operable by successive actuations of-anyv selecting switch to select any other telephone and supply ringingicurrent over the individual conev ductors of the selectingand selected telephones and talking current over the common conductors.

2. ,An intercommunication system comprising a plurality of telephones, a ringing bell for each telephone, a selecting switch and a ringing switch ateach telephone, ,a pair of line conductors commonzto all telephones, and an individual conductor for eachtelephone, a central station to which said conductors lead, said station having means operable'by successive actuations of any selecting switch to selectany other telephone and supply ringing currentover the individual con-- ductors oi ,the selecting'and selected telephones and talking. current over the common conductors, each ringing bell having a condenser in series therewith. l p s 3. An; intercornmunication system comprising a plurality of telephones, a ringing bell for each telephone, a selecting switch and a ringing switch at each telephone, a pair of line conductors common to all telephones, and an individual conductor for each telephone, a central station to which said conductors lead, said station having means operable by sucoessiveactuations of any selecting switch to select any other telephone and supply ringing current over the individual conductors of the selecting and selected-telephones and talking current overthe commonconductors, the select switches having means establishing a shunt across their telephones when actuated.

4. An intercommunication-system comprising a plurality of telephones, a ringing bell for each telephone, ,a selecting switch and aringing switch at each telephone, a pairof line conductors common to all telephones, and an individual conductor for each-telephone, a central station to which said conductors lead, said station having means operable by successive actuations of any selecting switch to select any other telephone and supply ringing current over the individual conductors of the selecting and selected, telephones and talking current over the common conductors,

said central station having means to supply alternating current for ringing purposes only, and means to supply direct current for operating and talking .o V

5. In a system for selectively interconnecting any pair of a number .of telephones for direct talking; a bell for each telephone, a, central selecting station, each telephone being connected to the central station by three conductors, two of which'are common to all telephones, and are connected through the hook-switch contacts oi. the telephones to opposite terminals of the series connected receiver and transmitter of' each telephone, and the third of which is individual to each telephone, a select g switch and a ringing switch at each telephone, control and selecting relays at the stationactuated by the selecting switches to select adesired telephone and connect ringing current to its bell undercontrol of the ringing switch at theselecting telephone.

,6; In an ntp communicating system comprising a plurality of telephones and a central station, a ringing bell for each telephone, a selecting switch and a ringing switch operable by pushbuttons at each, telephone, three talking and signalling channels between one or more telephones and the central station, one of these channels providing means to supply. ringing current to the telephonesduring a ringing period; and current for holding certain central station relays durlng a. selecting period; v I

'7. In an intercommunicating system comprising. a plurality of telephones and a central station; a ringing bell for each telephone, a selecting switch and a ringing switch operable by pushbuttons ateach telephone, selecting means at the central, station controlled by said selecting switch, three talking and signalling channels between one or more telephones and the central station, one of said channels providing means to supply selecting current and ringing current under control of said push buttons, a

8.-, An intercommunication system comprising a plurality of telephones, a ringing bell for each telephone, a selecting switch and a ringing switch at each telephone, a pair of line: conductorsicommon to said telephones, and an individual conductor for each telephone, a central station to which said conductors lead, said station having means operable from any'selecting switch to select any other telephone and supply ringing current overtheindividual conductors of the selecting and selected telephones and talking current over the common conductors.

,9. An intercommunication system comprising a plurality of; telephones, a ringing bell for each telephone, a selecting switch and a ringing switch 'at each-telephone, a pair of line conductors common to said telephones, and an individual conductor'for each telephone, a central station to which said conductors lead, said station having means operable from any selecting switch to select any other telephone and supply ringing currentv over the individual conductors of the selectingand selected telephones and talking current over the common conductors, said ringing bells each having biasing means to prevent the bells tapping until the ringing switch is operated.

C V OSCAR M. LEICH. 

